setdisplay(320,240,32,1)
  paper(0xFFFFFF):ink(0x000000):pen(0x000000):cls
  circle(120,100,80)
for y=20 to 200:for x=30 to 150
   c1=getpixel(x,y)
   c2=0xFFFFFF-c1
   ink(c2)
   dot(320-x,y)
     if key(27)<>0 then:end:end if
    waitvbl
 next:next
waitkey